Scheduling and transmitting uplink packets within uplink sub-frames ofa wireless system

ABSTRACT

A method and apparatus of scheduling and transmitting uplink packets within uplink sub-frames of a wireless system is disclosed. The method includes determining a size of a standard data unit, and determining if the standard data unit can be transmitted within a single sub-channel of an uplink frame by comparing the size of the standard data unit with a number of bits that can be transmitted within the uplink frame as determined by an uplink quality. If the standard data unit is too large to be transmitted within a single sub-channel of an uplink frame, then the standard data unit is divided into sub-data units. The sub-data units are transmitted over multiple uplink frames.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/804,201, filed May 17, 2007, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Described Embodiments

The described embodiments relate generally to wireless communications.More particularly, the described embodiments relate to a method andapparatus for scheduling and transmitting uplink packets within uplinksub-frames of a wireless system.

2. Background

Wireless communication protocols typically defined how wireless data isto be transmitted. A transmission parameter that can be standardized isthe minimum size data unit that can be transmitted. Another transmissionparameter can be standardized is scheduling for downlink (base stationto subscriber) and uplink (subscriber to base station) transmission.Typically, the scheduling generally determines how and when the minimumsize data unit is transmitted between the base station and thesubscriber.

Wireless network are subject to environmental influences that can causethe quality of links between base stations and subscribers to varygreatly. Generally, as wireless link quality decreases, the order ofmodulation of transmission signals must decrease, and the level ofcoding must increase. Therefore, for poor wireless links, the minimumsize data units may not fit within a scheduled uplink or downlink frame.

Mobile wireless systems generally include link qualities that vary morethan non-mobile wireless systems. Therefore, mobile wireless systems,such as, mobile WiMAX systems can require additional coordination ofsignal transmission between base stations and subscribers.

It is desirable to provide coordination of uplink transmission of WiMAXstandard packets through poor quality uplinks.

BRIEF SUMMARY OF THE INVENTION

An embodiment includes a method of scheduling and transmitting of uplinkpackets within uplink sub-frames of a wireless system. The methodincludes determining a size of a standard data unit. A number of bitsthat can be transmitted within each of the uplink frames is determinedbased on a quality of the uplink. A determination of whether thestandard data unit can be transmitted within a single sub-channel of anuplink frame is made by comparing the size of the standard data unitwith the number of bits that can be transmitted within the uplink frame.If the standard data unit is too large to be transmitted within a singlesub-channel of an uplink frame, then the standard data unit is dividedinto sub-data units. The sub-data units are transmitted over multipleuplink frames.

Another embodiment includes a method of a wireless system scheduling andtransmitting of uplink packets within uplink sub-frames of a wirelesssystem. The method includes a base station of the wireless systemproviding a size of a standard data unit. A number of bits that can betransmitted within each of the uplink sub-frames is determined by anuplink quality. Whether the standard data unit can be transmitted withina single sub-channel of the uplink sub-frames is determined by comparingthe size of the standard data unit with the number of bits that can betransmitted within the uplink sub-frame. If the standard data unit istoo large to be transmitted within a single sub-channel of an uplinksub-frame, then the standard data unit is divided into sub-data units. Asubscriber unit transmits the sub-data units over multiple uplinksub-frames.

Another embodiment includes another method of a wireless subscriberscheduling and transmitting of uplink packets within uplink sub-framesof a wireless system. The method includes determining a size of astandard data unit. Whether the standard data unit can be transmittedwithin a single sub-channel of an uplink sub-frame is determined bycomparing the size of the standard data unit with a number of bits thatcan be transmitted within the uplink sub-frame as determined by anuplink quality. If the standard data unit is too large to be transmittedwithin a single sub-channel of an uplink sub-frame, then the standarddata unit is divided into sub-data units. The sub-data units aretransmitted over at least one of multiple sub-channels of a singleuplink sub-frame, or over multiple uplink sub-frames.

Other aspects and advantages of the described embodiments will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, illustrating by way of example theprinciples of the described embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a WiMAX base station communicating with a subscriberthrough an uplink and a downlink.

FIG. 2 shows an example of a standard WiMAX data unit.

FIG. 3 shows an example of an uplink frame including sub-channels andtime slots.

FIG. 4 is a table showing modulation formats, bytes per symbol slot, andthe corresponding number of bytes that can be transmitted in five uplinkslots.

FIG. 5 is a flow chart that includes steps of one embodiment of a methoda wireless subscriber scheduling and transmitting uplink packets withinuplink sub-frames of a wireless system.

FIG. 6 shows an uplink frame that includes mini-sub-channels.

FIG. 7 is a flow chart that includes steps of one embodiment of a methodof a wireless system scheduling and transmitting uplink packets withinuplink sub-frames of a wireless system

FIG. 8 is a flow chart that includes the steps of another embodiment ofa method a wireless subscriber scheduling and transmitting uplinkpackets within uplink sub-frames of, a wireless system.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of methods and apparatuses for scheduling uplinktransmission between a base station and a subscriber are described. Theembodiments can include varying levels of transmission signal power, orvarying levels of processing power.

FIG. 1 shows a WiMAX base station 105 communicating with a subscriber115 through a channel (H) 110, that includes an uplink and a downlink.WiMAX protocol communication includes standard transmission protocols,such as, a MAC (media access control) PDU (protocol data unit). Theuplink transmission can be between a subscriber and a single basestation, or as will be described, between a subscriber and multiple basestations. The base station 105 and the subscriber 115 are shown withmultiple antennas. Some of the embodiments described utilize themultiple antennas, while other embodiments do not utilize the multipleantennas.

FIG. 2 shows an example of a standard WiMAX data unit. The WiMAX dataunit, generally referred to as the MAC PDU may include a MAC header 210,a sub-header 220, encryption 230, encrypted payload 240, ciphertextmessage authentication 250 and a CRC (cyclic redundancy check) 260. Thesize of an exemplary MAC PDU is 22 bytes plus an additional number ofbytes as determined by the data payload size. With payload, the MAC PDUcan typically include 30 to 60 bytes depending upon the size of thepayload.

FIG. 3 shows an example of an uplink frame including sub-channels andtime slots. In 802.16e OFDMA systems, several OFDM symbols maybededicated for uplink transmission. In a PUSC mode in 802.16e OFDMA, anuplink slot is composed of 1 sub-channel and 3 OFDMA symbols. That is,15 symbols occupy 5 slots, which correspond to the number of slots of asingle sub-channel. Depending upon the order of modulation and coding ofthe symbols, varying numbers of bytes can fits within the 5 slots of asingle sub-channel.

FIG. 4 is a table showing modulation and coding selection (MCS) scheme,bytes per symbol slot, and the corresponding number of bytes that can betransmitted in five uplink slots. As shown, an MCS scheme QPSK, 1/12coding allows for 1 byte per slot, or 5 bytes for the 5 slots. An MCSscheme QPSK, ⅛ coding allows for 1.5 bytes per slot, or 7.5 bytes forthe 5 slots. An MCS scheme QPSK, ¼ coding allows for 3.0 bytes per slot,15 bytes for the 5 slots. An MCS scheme QPSK, ½ coding allows for 6.0bytes per slot, 30 bytes for the 5 slots. An MCS scheme QPSK, ¾ codingallows for 9.0 bytes per slot, 45 bytes for the 5 slots. An MCS scheme16-QAM, ½ coding allows for 12.0 bytes per slot, 60 bytes for the 5slots. An MCS scheme 16-QAM, ¾ coding allows for 18.0 bytes per slot, 90bytes for the 5 slots. An MCS scheme 64-QAM, ½ coding allows for 18.0bytes per slot, 90 bytes for the 5 slots. An MCS scheme 16-QAM, ½ codingallows for 12.0 bytes per slot, 60 bytes for the 5 slots. The MCSschemes that include fewer than 30 bytes per 5 slots probably cannottransmit a single MAC PDU within a single sub-channel of an 802.16uplink frame. Therefore, without modification of the size of thestandard MAC PDU, the subscriber may not be complete a link with a basestation if the quality of the link is poor enough to require the MCSscheme to be QPSK, 1/12 coding because the MAC PDU may be too large tofit within a single sub-channel of the uplink frame.

FIG. 5 is a flow chart that includes steps of one embodiment of a methodof a wireless subscriber scheduling and transmitting uplink packetswithin uplink sub-frames of a wireless system. A first step 510 includesdetermining a size of a standard data unit. A second step 520 includesdetermining a number of bits that can be transmitted within each of theuplink sub-frames as determined by an uplink quality. A third step 530includes determining if the standard data unit can be transmitted withina single sub-channel of the uplink sub-frames by comparing the size ofthe standard data unit with the number of bits that can be transmittedwithin the uplink sub-frame. If the standard data unit is too large tobe transmitted within a single sub-channel of an uplink sub-frame, thena fourth step 540 includes dividing the standard data unit into sub-dataunits. A fifth step 550 includes transmitting the sub-data units overmultiple uplink sub-frames.

Standard Data Unit

The size of the standard data unit is generally determined by acommunications protocol standard, such as, the WiMAX standard in whichthe standard data unit is a WiMAX standard MAC PDU. For one embodimentof a wireless system, the size of a standard data unit is received froman upstream base station. Another embodiment includes the subscribercalculating the size.

Number of Bits Transmitted within an Uplink Sub-Frame

Generally, the number of bits that can be transmitted within an UplinkSub-frame is dependent upon the quality of the uplink, and the number ofsymbols that can be included within an uplink sub-frame. Additionally,transmission channel bandwidth restrictions influence the number ofbits.

For an embodiment, the determining a number of bits that can betransmitted within the uplink sub-frame includes determining SINR ofsignals transmitted through the uplink, determining an uplink modulationformat based on the SINR, and calculating the number of bits that can betransmitted within the uplink sub-frame based on the uplink modulationformat and a number of available symbol slots within the uplinksub-frame. Generally, the base station provides the number of slots persub-frame. The number of bits within each transmitted symbol isdependent upon the SNR of signals transmitted through the link. That isthe better the SINR, the higher the possible order of modulation of thesymbols.

Therefore, knowing the SINR and the number of available time slots persub-frame allows determination of the number of bits per sub-frame. Oncethe number of bits per sub-frame has been determined, and the size(number of bits) of a standard data unit, a determination of how todivide the standard data unit into sub-data units can be made. Morespecifically, once the number of bytes can be transmitted in each uplinksub-frame has been determined, the number of sub-data units can bedetermined by dividing the size of the standard data unit by the numberof bytes that can be transmitted in each uplink sub-frame.

Encoding of the Sub-Data Units

Generally, there are two embodiments for encoding the sub-data units. Afirst embodiment includes dividing the standard data units into sub-dataunits, and then encoding each of the individual sub-data units. A secondembodiment includes encoding the standard data units before dividingthem up into sub-data units. Either way, the encoding adds additionalbits for transmission.

If a standard data unit is determined to be too large for a singlesub-channel of an uplink frame, and the standard data unit is dividedinto sub-data units, the sub-data units can be transmitted over multipleuplink frames, or over multiple channels of a single frame, eachapproach has advantages and disadvantages. Transmitting over multipleframes can allow for transmission over a single sub-channel, which canbe advantageous over multiple sub-channels because the transmissionpower is limited by an average power level. Therefore, by transmittingover a narrower frequency band, the transmission power per sub-carriercan be greater than transmitting over a wider frequency band. Additionalincreases in transmission power per sub-carrier can be achieved bydividing the standard sub-channels into mini-sub-channels. Generally,the reduced bandwidth of a mini-sub-channel allows for an increase inSNR, and therefore, an increase in the order of modulation of thetransmitted signals.

An embodiment includes dividing the sub-channel in to mini-sub-channels,and determining how many bytes can be transmitted within an uplinksub-frame of each mini-sub-channel. The standard units can be dividedinto sub-data units, wherein a size of the sub-data units is dependenton many bytes can be transmitted within a mini-sub-channel uplinksub-frame. Depending upon the size of the standard data unit and howmany bytes can be transmitted within an uplink sub-frame of eachmini-sub-channel, the sub-data units are transmitted over multipleuplink sub-frames, over mini-sub-channels.

Each sub-data unit can include at least one indicator bit for aiding thebase station in reconfiguring the standard data units from the sub-dataunits. One embodiment of the indicator bits indicates whether thestandard data unit of the sub-data unit starts in a present transmissionburst and continues into a next transmission burst, the standard dataunit of the sub-data unit starts continues from a previous transmissionburst and continues into a next transmission burst, the standard dataunit of the sub-data unit starts continues from a previous transmissionburst and ends within the present transmission burst. Generally, a burstcan be defined as a continuous set of time and frequency slots asdetermined by a transmission scheduler.

Communication Diversity

Transmission diversity of several forms can be achieved by dividing thestandard data units into sub-data units. Spreading the sub-data unitsover multiple uplink frames provides time diversity. Spreading thesub-data units over multiple sub-channels or over multiple mini-subchannels provides frequency diversity. The subscriber units can includemultiple antennas. Therefore, spatial diversity can be achieved bytransmitting sub-data units of a standard data unit over differentantennas. That is, each of the sub-data units of successive uplinksub-frames can be transmitted through different of the multipleantennas. For a given uplink sub-frame, the sub-data units can besimultaneously transmitted over multiple of the different antennas, andtherefore, transmission can be over different multiple antennas forsuccessive uplink sub-frames. Alternative or additional spatialdiversity includes the subscriber transmitting to multiple basestations. The multiple base stations coordinate their reception torecombine the sub-data units back into standard protocol data units.

For another embodiment the subscriber determines whether each sub-dataunit is received by a base station. If the subscriber determines that asub-data unit is not received by the base station, the subscriberincreasing a transmission power level of one or more subsequentlytransmitted sub-data units.

FIG. 6 shows an uplink frame that includes mini-sub-channels. Dividingthe sub-channels into smaller bandwidth mini-sub-channels allows for anincrease in the transmission power level of the subscriber. As shown,each min-sub-channel includes fewer than k sub-carriers. Due to thepossible increase in transmission power, a power amplifier used fortransmission of the sub-data units over the mini-sub-channels can reduceits power back-off.

FIG. 7 is a flow chart that includes the steps of another embodiment ofa wireless system scheduling and transmitting uplink packets withinuplink sub-frames of a wireless system. A first step 710 includes a basestation of the wireless system providing a size of a standard data unit.A second step 720 includes determining a number of bits that can betransmitted within each of the uplink sub-frames as determined by anuplink quality. A third step 730 includes determining if the standarddata unit can be transmitted within a single sub-channel of the uplinksub-frames by comparing the size of the standard data unit with thenumber of bits that can be transmitted within the uplink sub-frame. Ifthe standard data unit is too large to be transmitted within a singlesub-channel of an uplink sub-frame, then a fourth step 740 includesdividing the standard data unit into sub-data units. A fifth step 750includes a subscriber unit transmitting the sub-data units over multipleuplink sub-frames.

For an embodiment of a wireless system, the base station schedulestransmission of the sub-protocol data units, by specifying sub-channelsand time slots of multiple uplink sub-frames. According to the schedule,the base station receives and buffers the sub-data units. The based thenre-combines the sub-data units re-forming the standard data units. Thiscan include each sub-data unit being transmitted using HARQ. Eachsub-data unit is retransmitted when the base station transmits a NAK forthe sub-data unit, and the base station reassembling the sub-protocoldata units back into standard data units.

Multiple Uplink Base Stations

Additional or alternative spatial diversity can be obtained by havingmultiple base stations receiving sub data units transmitted by thesubscriber. The multiple base stations reconfigure the sub data units toobtain the original standard data units. For example, one embodimentincludes the base station and a second base station simultaneouslyreceiving sub-data units from the subscriber, coordinating reception ofthe base station and the second base station, and reconfiguring thesub-data units forming the original standard data units. For anotherembodiment, the base station and the second base station receivedifferent sub-data units.

FIG. 8 is a flow chart that includes the steps of another embodiment ofa method a wireless subscriber scheduling and transmitting uplinkpackets within uplink sub-frames of a wireless system. A first step 810includes determining a size of a standard data unit. A second step 820includes determining if the standard data unit can be transmitted withina single sub-channel of an uplink sub-frame by comparing the size of thestandard data unit with a number of bits that can be transmitted withinthe uplink sub-frame as determined by an uplink quality. If the standarddata unit is too large to be transmitted within a single sub-channel ofan uplink sub-frame, then a third step 830 includes dividing thestandard data unit into sub-data units. A fourth step 840 includestransmitting the sub-data units over at least one of multiplesub-channels of a single uplink sub-frame, or over multiple uplinksub-frames.

Depending upon whether the wireless subscriber is transmission powerlimited or processing power limited, the sub-data units can be spreadover multiple sub-channels or over multiple sub-frames. If thesubscriber is power consumption limited, then the sub-data units can betransmitted over multiple sub-channels of a single uplink sub-frame. Ifthe subscriber is transmission power limited, then the sub-data unitscan be transmitted over multiple uplink sub-frames.

Although specific embodiments have been described and illustrated, theembodiments are not to be limited to the specific forms or arrangementsof parts so described and illustrated. The embodiments are limited onlyby the appended claims.

1. A method of a wireless subscriber scheduling and transmitting ofuplink packets within uplink sub-frames of a wireless system,comprising: determining a size of a standard data unit; determining ifthe standard data unit can be transmitted within a single sub-channel ofan uplink sub-fume by comparing the size of the standard data unit witha number of bits that can be transmitted within the single sub-channelof the uplink sub-frame; and if the size of the standard data unitexceeds the number of bits that can be transmitted within the singlesub-channel of the uplink sub-frame, then: determining whether thewireless subscriber is transmission power limited or processing powerlimited; dividing the standard data unit into sub-data units; andtransmitting the sub-data units over multiple uplink sub-frames or overmultiple sub-channels within the uplink sub-frame depending on whetherthe wireless subscriber is determined to be transmission power limitedor processing power limited.
 2. The method of claim 1, wherein thesub-data units are transmitted over the multiple uplink sub-frames whenthe wireless subscriber is determined to be transmission power limited.3. The method of claim 1, wherein the sub-data units are transmittedover the multiple sub-channels of the uplink sub-frame when the wirelesssubscriber is determined to be processing power limited.
 4. The methodof claim 2, wherein the sub-data units are transmitted over a singlesub-channel within the multiple uplink sub-frames when the wirelesssubscriber is determined to be transmission power limited.
 5. The methodof claim 1, further comprising determining how many bytes can betransmitted within each uplink sub-frame or each sub-channel dependingon whether the wireless subscriber is determined to be transmissionpower limited or processing power limited.
 6. The method of claim 5,wherein a size of the sub-data units is dependent on how many bytes canbe transmitted within each uplink sub-frame or each sub-channel,depending on whether the wireless subscriber is determined to betransmission power limited or processing power limited.
 7. The method ofclaim 1, further comprising: dividing the sub-channel of the uplinksub-frame into mini-sub-channels; and transmit the sub-data units overthe mini-sub-channels when the wireless subscriber is determined to beprocessing power limited.
 8. The method of claim 7, further comprising:reducing power back-off of a power amplifier used for transmission ofthe sub-data units when the sub-data units are transmitted over themini-sub-channels within the uplink sub-frame.
 9. The method of claim 1,wherein the sub-data units are transmitted over different ones of aplurality of antennas.
 10. The method of claim 1, wherein differentsub-data units are transmitted to different base stations.
 11. Themethod of claim 1, further comprising: determining whether a firstsub-data unit was received by a base station; and if it is determinedthat the first sub-data unit was not received by the base station,increasing a transmission power for transmission of a second sub-dataunit.
 12. The method of claim 1, wherein dividing the standard data unitcomprises dividing each standard data unit and separately encoding eachsub-data unit.
 13. The method of claim 1, wherein dividing the standarddata unit comprises encoding the standard data unit, and dividing theencoded standard data unit into sub encoded data units.
 14. The methodof claim 1, wherein the sub-data units are transmitted according to atransmission schedule received from a base station.
 15. The method ofclaim 14, further comprising: receiving a non-acknowledgement signalfrom a base station that a first sub-data unit was not received by thebase station; and retransmitting the first sub-data unit.
 16. The methodof claim 15, wherein the non-acknowledgement signal is generated basedon a comparison of received information to the transmission schedule.17. The method of claim 1, further comprising: a plurality of basestations simultaneously receiving the sub-data units from the wirelesssubscriber; coordinating reception of the sub-data units between theplurality of base stations; and reconfiguring the sub-data units to formthe original standard data units.